Vaillant Eco Tec 824 pressure increasing on heating

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The heating switches off, as the display starts to flash the current pressure

 

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Back at this job today, checked the new expansion vessel, was at 0.75 topped it to 1bar. Check the copper tubes connected to it, all clean. Called Vaillant technical and even they anit for a clue what it could be now.
Fobbed me off with a blockage issue. Even tho I explained that I powerflushed the system only a year ago. I spent a very long time on it, so I know its not that. Also there is a magna clean fitted on the boiler.
Has any1 got any suggestions??

 

[TBServices]

Back at this job today, checked the new expansion vessel, was at 0.75 topped it to 1bar. Check the copper tubes connected to it, all clean. Called Vaillant technical and even they anit for a clue what it could be now.
Fobbed me off with a blockage issue. Even tho I explained that I powerflushed the system only a year ago. I spent a very long time on it, so I know its not that. Also there is a magna clean fitted on the boiler.
Has any1 got any suggestions??

The powerflush could have actually made the situation worse if you've loosened a load of gunk that didnt manage to get flushed out and it's got stuck somewhere.

 

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If that was the case I don't think the boiler would have worked for this long.
It was done in November 2011.

 

[wards]

just a thought,have any rads been replaced or more rads been added?

 

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Nope the system is the same. No radiators added or taken away.
I've disconnected the filling loop and told the customer not to use the heating.
Filled the system to 0.8bar.
I got a feeling could be a very small pin hole in the domestic heat exchanger.
Let's wait a see......

 

[wards]

silly question but i take it you cleaned out the magnaclean?

 

[jtsplumbing]

Just use a foot pump with gauge, but what i have done is fit a longer hose on to pump,(2Mtrs) used same method for years.

 

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I wanted to but the customer didnt have the key. The lid was very tight, no chance of opening it, wothout a key. But I don't think there is much on there as I opened the filter in the flow pipe and that was clean. I'm gonna give it a day and wait for the feedback from the customer

 

[arran197]

How big is this system? If it's too big, the vessel won't cope.

 

[buckley plumb]

you could fit an external vessel or easier just to try and check isolate one radioator and drain it . then only open one valve so rad acts as a large expansion vessel as temp measure and see if the pressure still rises if not you have found the issue

 

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Just had an update from the customer. It was a faulty dhw heat exchanger. The orignal pressure vessel tank had no pressure.
brought a new Regin pump and pumped the original tank to 1bar, and replaced the heat exchanger.
So glad it's sorted.
Thanks guys for all your help.